Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$45.68	5.866%	$48.3596	$48.36	$48.35	$48.40
Purchase #2	$78.92	3.713%	$81.8503	$81.85	$81.85	$81.90
Purchase #3	$169.34	9.377%	$185.219	$185.22	$185.20	$185.20
Purchase #4	$81.92	9.630%	$89.8089	$89.81	$89.80	$89.80
Purchase #5	$70.85	3.320%	$73.2022	$73.20	$73.20	$73.20
Purchase #6	$143.49	9.335%	$156.8848	$156.88	$156.90	$156.90
Purchase #7	$123.69	13.379%	$140.2385	$140.24	$140.25	$140.20
7 purchase totals =	$713.89		$775.5633	$775.56	$775.55	$775.60